don't waste any real money trying to get that fixed. A few hundred maybe if you want, but not $1k.

The shop told you the right thing. The rust is forming at the seam, and likely coming from inside the welds to the outside. You can sand it down and repaint it, but the rust has "infected" the panel and will come back eventually.

One shop I went to for an estimate was going to cut out the rusted piece and weld in a patch panel. I know rust is a cancer for cars, but (hopefully) if they do the job right, you should be able to cut it out and not have any future problems, just like restoring any old car. Even if I had to pay $1500 to get it cut out, re-painted, and repaired properly, it would still be cheaper than buying a new car (with a $400/month car payment). That is really the only reason I have been looking to get it repaired rather than just scrap the car and buy a new one (plus there aren't many that I like out right now that are in my price range....). and I only have 83,000 miles, so hopefully the engine will still last for awhile. I was hoping to get another 3-4 years out of the car, but if I leave the rust unchecked, I think it will eventually be un-sellable or un-tradeable when I eventually get a new car.